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Beacon Station No 1641 July 10 2003 <br /> Stockton California Preliminary Results Report and Work Plan Addendum <br /> SITE DESCRIPTION AND BACKGROUND <br /> Beacon Station No 3641 is an operating service station located on the southwest corner of <br /> the intersection of East Hammer Lane and Kathleen Drive in Stockton, California as shown <br /> on Figure 1 The parcel is located in a commercially zoned area and is known to the San <br /> Joaquin County assessor as APN 094-03-12 Site facilities include a service <br /> station/convenience store, two canopy-covered dispenser islands situated in the central <br /> portion of the property, and three double-walled underground storage tanks (USTs) located <br /> in the western portion of the property The locations of these facilities and other pertinent <br /> site features are shown on Figure 2 <br /> In June 1996, four steel single-walled, 10,000-gallon unleaded gasoline USTs (T-1 through <br /> T-4) were excavated and removed from a common basin at the site Associated dispenser <br /> and product lines were also removed with the UST systems The UST cavity was over- <br /> excavated to 19 feet bsg beneath former USTs T-1 and the west half of T-2 Additional <br /> • over-excavation could not be conducted because of the proximity of the sidewalk and street <br /> Soil analytical results indicated total petroleum hydrocarbons as gasoline (TPHg) <br /> concentrations to 6,800 milligrams per kilogram (parts per million or ppm) and benzene <br /> concentrations to 80 ppm at depths of 14 to 19 feet beneath former USTs T-1 and T-2 <br /> Two 10,000-gallon and one 12,000-gallon, double-walled, fiberglass-clad steel USTs were <br /> installed in the former UST basin in June 1996 During installation of the new USTs, ten <br /> 18-inch diameter conductor casings were installed in the former UST cavity to facilitate <br /> future assessment and/or confirmation drilling through the backfilled UST cavity <br /> In July 1996, Horizon drilled soil borings B-1 and B-2 through two of the UST cavity <br /> conductor casings Groundwater was encountered in the borings at depths of approximately <br /> 64 feet bsg Soil boring B-1 was completed as dual soil vapor extraction well VW-3NW-4 <br /> Soil boring B-2 was completed as groundwater monitoring well MW-1 and dual vapor <br /> . extraction well VW-1NW-2 <br /> WPadd=7-03 <br /> ProjeetNo 1641 16 2 HORIZON ENVIRONMENTAL INC <br />